In general, in one aspect, the invention features a data structure representing a schedule for a plurality of N resources, and apparatus, methods, and computer programs for generating and using the data structure, the data structure comprising: M records each representing a different one of M slots in the schedule, wherein M>1, wherein each of the M slots is allocated to one of the N resources, and wherein each of the M records comprises identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record, and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

Claim:

What is claimed is:

1. An apparatus comprising: a memory to store a scheduling data structure for a schedule for N resources, wherein: N>1; the scheduling data structure comprises M records; M>1; each of the M records represents a different one of M slots in the schedule; and each of the M slots is allocated to one of the N resources; and a scheduler comprising: a read circuit to read a record indicated by an index; a select circuitto select the resource allocated to the slot represented by the record read by the read circuit; and an index circuit to generate the index based on a previous record read by the read circuit, wherein: the index circuit comprises: an availabilitycircuit to determine which of the N resources are available; a next available resource circuit to select the available resource that occurs next in the schedule based on the previous record; and a resource order circuit to identify the recordrepresenting the next slot allocated to the selected available resource based on the previous record, and to generate the index to indicate the identified record; each of the N resources occurs in the schedule WN times; and .times..times. ##EQU00009##

2. The apparatus of claim 1, wherein each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

3. The apparatus of claim 2, wherein: the identifier of the order in which the N resources occur in the schedule comprises a sequence of N fields for each of the M records; and each of the N fields comprises an identifier of a respective oneof the N resources.

4. The apparatus of claim 3, wherein the identifiers of the N resources are coded as one-hot binary numbers.

5. The apparatus of claim 1, further comprising the N resources.

6. The apparatus of claim 5, wherein: each of the resources comprises a buffer for packets of data; and the apparatus transmits one or more of the packets of data when the corresponding resource is selected.

7. The apparatus of claim 6, wherein the apparatus is a network device, and the network device is selected from a group consisting of: a switch; a router; and a network interface controller.

8. The apparatus of claim 6, wherein the apparatus is a wireless network device, and the wireless network device is compliant with at least one standard selected from a group consisting of IEEE standards 802.11, 802.11a, 802.11b, 802.11g,802.11n, 802.16, and 802.20.

9. An apparatus comprising: means for storing a scheduling data structure for a schedule for N resources, wherein: N>1; the scheduling data structure comprises M records; M>1; each of the M records represents a different one of M slotsin the schedule; and each of the M slots is allocated to one of the N resources; and means for scheduling comprising: means for reading a record indicated by an index; means for selecting the resource allocated to the slot represented by the recordread by the means for reading; and means for generating the index based on a previous record read by the means for reading, wherein: the means for generating comprises: means for determining which of the N resources are available; means for selectingthe available resource that occurs next in the schedule based on the previous record; means for identifying the record representing the next slot allocated to the selected available resource based on the previous record; and means for generating theindex to indicate the identified record; each of the N resources occurs in the schedule W.sub.N times; and .times..times. ##EQU00010##

10. The apparatus of claim 9, wherein each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by therecord; and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

11. The apparatus of claim 10, wherein: the identifier of the order in which the N resources occur in the schedule comprises a sequence of N fields for each of the M records; and each of the N fields comprises an identifier of a respective oneof the N resources.

12. The apparatus of claim 11, wherein the identifiers of the N resources are coded as one-hot binary numbers.

13. The apparatus of claim 9, further comprising the N resources.

14. The apparatus of claim 13, wherein: each of the resources comprises a buffer for packets of data; and the apparatus transmits one or more of the packets of data when the corresponding resource is selected.

15. The apparatus of claim 14, wherein the apparatus is a network device, and the network device is selected from a group consisting of: a switch; a router; and a network interface controller.

16. The apparatus of claim 14, wherein the apparatus is a wireless network device, and the wireless network device is compliant with at least one standard selected from a group consisting of IEEE standards 802.11, 802.11a, 802.11b, 802.11g,802.11n, 802.16, and 802.20.

17. A method performed by a scheduler comprising: (a) selecting one of M records in a scheduling data structure comprising M of the records, wherein: M>1; each of the M records represents a different one of M slots in a schedule; each ofthe M slots is allocated to one of N resources; and N>1; (b) selecting the resource allocated to the slots represented by the selected record; and (c) selecting a subsequent record comprising: determining which of the N resources are available; selecting the available resource that occurs next in the schedule based on the record selected in step (a); and identifying the record representing the next slot allocated to the selected available resource based on the record selected in step (a),wherein: each of the N resources occurs in the schedule W.sub.N times; and .times..times. ##EQU00011##

18. The method of claim 17, further comprising repeating steps (b) and (c).

19. The method of claim 17, wherein: each of the resources represents packets of data; and the method further comprises transmitting one or more of the packets of data represented by the selected resource.

20. The method of claim 17, wherein each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

21. The method of claim 20, wherein: the identifier of the order in which the N resources occur in the schedule comprises a sequence of N fields for each of the M records; and each of the N fields comprises an identifier of a respective one ofthe N resources.

22. The method of claim 21, wherein the identifiers of the N resources are coded as one-hot binary numbers.

23. A non-transitory tangible computer readable storage medium encoded with a computer program and executable by a computer, the computer program comprising instructions for: (a) selecting one of M records in a scheduling data structurecomprising M of the records, wherein: M>1; each of the M records represents a different one of M slots in a schedule; each of the M slots is allocated to one of N resources; and N>1; (b) selecting the resource allocated to the slots representedby the selected record; and (c) selecting a subsequent record comprising: determining which of the resources are available; selecting the available resource that occurs next in the schedule based on the record selected in step (a); and identifying therecord representing the next slot allocated to the selected available resource based on the record selected in step (a), wherein: each of the N resources occurs in the schedule W.sub.N times; and .times..times. ##EQU00012##

25. The computer readable storage medium of claim 23, wherein: each of the resources represents packets of data; and the computer program_further comprises instructions for causing transmission of one or more of the packets of data representedby the selected resource.

26. The computer readable storage medium of claim 23, wherein each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slotsrepresented by the record; and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

27. The computer readable storage medium of claim 26, wherein: the identifier of the order in which the N resources occur in the schedule comprises a sequence of N fields for each of the M records; and each of the N fields comprises anidentifier of a respective one of the N resources.

28. The computer readable storage medium of claim 27, wherein the identifiers of the N resources are coded as one-hot binary numbers.

29. A method performed by a scheduler comprising: identifying a schedule for N resources, where N>1; generating a data structure representing the schedule for the N resources; generating M records each representing a different one of Mslots in the schedule, where M>1, wherein each of the M slots is allocated to one of the N resources; generating for each of the M records identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the Nresources following the one of the M slots represented by the record; and generating for each of the M records an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record, wherein:each of the N resources occurs in the schedule W.sub.N times; and .times..times. ##EQU00013##

30. The method of claim 29, wherein: generating the identifier of the order in which the N resources occur in the schedule comprises generating a sequence of N fields for each of the M records; and each of the N fields comprises an identifierof a respective one of the N resources.

31. The method of claim 30, further comprising: encoding the identifiers of the N resources as one-hot binary numbers.

32. The method of claim 29, further comprising receiving the schedule, wherein: the schedule comprises M entries; and each of the M entries represents one of the M slots and the one of the N resources scheduled for the one of the M slots.

33. The method of claim 29, further comprising: identifying the N resources; and generating the schedule comprising generating M entries, wherein each of the M entries represents one of the M slots and the one of the N resources scheduled forthe one of the M slots.

34. The method of claim 33, further comprising: identifying a weight W.sub.N for each of the N resources; and generating the schedule based on the weights W.sub.N.

35. A non-transitory tangible computer readable storage medium encoded with a computer program and executable by a computer, the computer program comprising instructions for: identifying a schedule for N resources, where N>1; and generatinga data structure representing the schedule for the N resources; generating M records each representing a different one of M slots in the schedule, where M>1, wherein each of the M slots is allocated to one of the N resources; generating for each ofthe M records identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and generating for each of the M records an identifier of anorder in which the N resources occur in the schedule following the one of the M slots represented by the record wherein: each of the N resources occurs in the schedule W.sub.N times; and .times..times. ##EQU00014##

36. The computer readable storage medium of claim 35, wherein: generating the identifier of the order in which the N resources occur in the schedule comprises generating a sequence of N fields for each of the M records; and each of the Nfields comprises an identifier of a respective one of the N resources.

37. The computer readable storage medium of claim 36, wherein the computer program, further comprises instructions for encoding the identifiers of the N resources as one-hot binary numbers.

38. The computer readable storage medium of claim 35, wherein the computer program, further comprises instructions for receiving the schedule, wherein: the schedule comprises M entries and each of the M entries represents one of the M slots andthe one of the N resources scheduled for the one of the M slots.

39. The computer readable storage medium of claim 35, wherein the computer program, further comprises instructions for: identifying the N resources; and generating the schedule comprising generating M entries, wherein each of the M entriesrepresents one of the M slots and the one of the N resources scheduled for the one of the M slots.

40. The computer readable storage medium of claim 39, wherein the computer program further comprises instructions for: identifying a weight W.sub.N for each of the N resources; and generating the schedule based on the weights W.sub.N.

41. The apparatus of claim 1, wherein the index circuit generates the index based on the previous record read by the read circuit before reading the record indicated by the index.

42. The apparatus of claim 1 wherein: the index circuit generates the index based only on the previous record; and the read circuit conducts only a single read operation for each one of the M slots.

43. The apparatus of claim 1, wherein the record indicated by the index is not constructed from the previous record.

In general, in one aspect, the invention features a memory to store a scheduling data structure for a schedule for N resources, wherein N>1, the scheduling data structure comprising M records, wherein M>1, wherein each of the M recordsrepresents a different one of M slots in the schedule, and wherein each of the M slots is allocated to one of N resources; and a scheduler comprising a read circuit to read the record indicated by an index, a select circuit to select the resourceallocated to the slot represented by the record read by the read circuit, and an index circuit to generate the index based on a previous record read by the read circuit, comprising an availability circuit to determine which of the resources areavailable, a next available resource circuit to select the available resource that occurs next in the schedule based on the previous record, and a resource order circuit to identify the record representing the next slot allocated to the selectedavailable resource based on the previous record, and to generate the index to indicate the identified record.

In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00001## In some embodiments, each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented bythe record; and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record. In some embodiments, the identifier of the order in which the N resources occur in the schedulecomprises, for each of the M records: a sequence of N fields each comprising an identifier of a respective one of the N resources. In some embodiments, the identifiers of the N resources are coded as one-hot binary numbers. Some embodiments comprisethe N resources. In some embodiments, each of the resources comprises: a buffer for packets of data; wherein the apparatus transmits one or more of the packets of data when the corresponding resource is selected. Some embodiments comprise a networkdevice comprising the apparatus, wherein the network device is selected from the group consisting of: a switch; a router; and a network interface controller. Some embodiments comprise a wireless network device according to claim 8 which is compliantwith at least one standard selected from the group consisting of IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11n, 802.16, and 802.20.

In general, in one aspect, the invention features an apparatus comprising: means for storing a scheduling data structure for a schedule for N resources, wherein N>1, the scheduling data structure comprising M records, wherein M>1, whereineach of the M records represents a different one of M slots in the schedule, and wherein each of the M slots is allocated to one of N resources; and means for scheduling comprising means for reading the record indicated by an index, means for selectingthe resource allocated to the slot represented by the record read by the means for reading, and means for generating the index based on a previous record read by the means for reading, comprising means for determining which of the resources areavailable, means for selecting the available resource that occurs next in the schedule based on the previous record, means for identifying the record representing the next slot allocated to the selected available resource based on the previous record,and means for generating the index to indicate the identified record.

In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00002##

In some embodiments, each of the M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and an identifierof an order in which the N resources occur in the schedule following the one of the M slots represented by the record. In some embodiments, the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records:a sequence of N fields each comprising an identifier of a respective one of the N resources. In some embodiments, the identifiers of the N resources are coded as one-hot binary numbers. Some embodiments comprise the N resources. In some embodiments,each of the resources comprises: a buffer for packets of data; wherein the apparatus transmits one or more of the packets of data when the corresponding resource is selected. Some embodiments comprise a network device comprising the apparatus, whereinthe network device is selected from the group consisting of: a switch; a router; and a network interface controller. Some embodiments comprise a wireless network device according to claim 17 which is compliant with at least one standard selected fromthe group consisting of IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11n, 802.16, and 802.20.

In general, in one aspect, the invention features a method comprising: (a) selecting one of M records in a scheduling data structure comprising M of the records, wherein M>1, wherein each of the M records represents a different one of M slotsin a schedule, wherein each of the M slots is allocated to one of N resources, wherein N>1; (b) selecting the resource allocated to the slots represented by the selected record; and (c) selecting a subsequent record, comprising determining which ofthe resources are available, selecting the available resource that occurs next in the schedule based on the record selected in step (a), and identifying the record representing the next slot allocated to the selected available resource based on therecord selected in step (a). Some embodiments comprise repeating steps (b) and (c). In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00003## In some embodiments, each of the resources represents packets of data, further comprising: transmitting one or more of the packets of data represented by the selected resource. In some embodiments, each of the Mrecords comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and an identifier of an order in which the N resources occurin the schedule following the one of the M slots represented by the record. In some embodiments, the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records: a sequence of N fields each comprising anidentifier of a respective one of the N resources. In some embodiments, the identifiers of the N resources are coded as one-hot binary numbers.

In general, in one aspect, the invention features a computer program comprising: (a) selecting one of M records in a scheduling data structure comprising M of the records, wherein M>1, wherein each of the M records represents a different oneof M slots in a schedule, wherein each of the M slots is allocated to one of N resources, wherein N>1; (b) selecting the resource allocated to the slots represented by the selected record; and (c) selecting a subsequent record, comprising determiningwhich of the resources are available, selecting the available resource that occurs next in the schedule based on the record selected in step (a), and identifying the record representing the next slot allocated to the selected available resource based onthe record selected in step (a).

Some embodiments comprise repeating steps (b) and (c). In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00004## In some embodiments, each of the resources represents packets of data, further comprising: causing transmission of one or more of the packets of data represented by the selected resource. In some embodiments, each ofthe M records comprises: identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slots represented by the record; and an identifier of an order in which the N resourcesoccur in the schedule following the one of the M slots represented by the record. In some embodiments, the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records: a sequence of N fields eachcomprising an identifier of a respective one of the N resources. In some embodiments, the identifiers of the N resources are coded as one-hot binary numbers.

In general, in one aspect, the invention features a method comprising: identifying a schedule for N resources, wherein N>1; generating a data structure representing the schedule for the N resources, comprising generating M records eachrepresenting a different one of M slots in the schedule, wherein M>1, wherein each of the M slots is allocated to one of the N resources, comprising, for each of the M records generating identifiers of the N ones of the M slots in the scheduleallocated to a next occurrence of each of the N resources following the one of the M slots represented by the record, and generating an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented bythe record.

In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00005## In some embodiments, generating the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records: generating a sequence of N fields each comprising an identifier of arespective one of the N resources. Some embodiments comprise encoding the identifiers of the N resources as one-hot binary numbers. Some embodiments comprise receiving the schedule, wherein the schedule comprises M entries, each representing one of theM slots and the one of the N resources scheduled for the one of the M slots. Some embodiments comprise identifying the N resources; and generating the schedule, comprising generating M entries, each representing one of the M slots and the one of the Nresources scheduled for the one of the M slots. Some embodiments comprise identifying a weight WN for each of the N resources; and generating the schedule based on the weights WN.

In general, in one aspect, the invention features a computer program comprising: identifying a schedule for N resources, wherein N>1; generating a data structure representing the schedule for the N resources, comprising generating M recordseach representing a different one of M slots in the schedule, wherein M>1, wherein each of the M slots is allocated to one of the N resources, comprising, for each of the M records generating identifiers of the N ones of the M slots in the scheduleallocated to a next occurrence of each of the N resources following the one of the M slots represented by the record, and generating an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented bythe record.

In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00006## In some embodiments, generating the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records: generating a sequence of N fields each comprising an identifier of arespective one of the N resources. Some embodiments comprise encoding the identifiers of the N resources as one-hot binary numbers. Some embodiments comprise receiving the schedule, wherein the schedule comprises M entries, each representing one of theM slots and the one of the N resources scheduled for the one of the M slots. Some embodiments comprise identifying the N resources; and generating the schedule, comprising generating M entries, each representing one of the M slots and the one of the Nresources scheduled for the one of the M slots. Some embodiments comprise identifying a weight WN for each of the N resources; and generating the schedule based on the weights WN.

In general, in one aspect, the invention features a data structure representing a schedule for N resources, wherein N>1, the data structure comprising: M records each representing a different one of M slots in the schedule, wherein M>1,wherein each of the M slots is allocated to one of the N resources, and wherein each of the M records comprises identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the Mslots represented by the record, and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

In some embodiments, each of the N resources occurs in the schedule W.sub.N times; and

.times..times. ##EQU00007## In some embodiments, the identifier of the order in which the N resources occur in the schedule comprises, for each of the M records: a sequence of N fields each comprising an identifier of a respective one of the Nresources. In some embodiments, the identifiers of the N resources are coded as one-hot binary numbers.

The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 shows a programmable resource scheduling system for N resources, each of which may be available or unavailable, and a schedule having M slots, according to a preferred embodiment of the present invention.

FIG. 3 shows a data structure representing the schedule of FIG. 2 according to a preferred embodiment of the present invention.

FIG. 4 shows a process for generating the data structure of FIG. 3 according to a preferred embodiment of the present invention.

FIG. 5 shows a data communications system comprising a network switch in communication with a network according to a preferred embodiment of the present invention.

FIG. 6 shows a process for the scheduler of FIG. 5 according to a preferred embodiment of the present invention.

FIGS. 7A-7E show various exemplary implementations of the present invention.

The leading digit(s) of each reference numeral used in this specification indicates the number of the drawing in which the reference numeral first appears.

DETAILED DESCRIPTION

Embodiments of the present invention provide a data structure representing a schedule for N resources, wherein N>1. The data structure comprises M records each representing a different one of M slots in the schedule, wherein M>1, whereineach of the M slots is allocated to one of the N resources, and wherein each of the M records comprises identifiers of the N ones of the M slots in the schedule allocated to a next occurrence of each of the N resources following the one of the M slotsrepresented by the record, and an identifier of an order in which the N resources occur in the schedule following the one of the M slots represented by the record.

Some embodiments of the present invention provide an apparatus to use the data structure to select the resources according to the schedule. For example, according to a preferred embodiment of the present invention, a network switch implementingmultiple quality-of-service (QoS) levels employs the data structure to schedule the transmission of packets of data from the switch.

Some embodiments of the present invention provide an apparatus to generate the data structure based upon the schedule. For example, a customer can provide a schedule comprising a sequence in which the resources are to be selected. The datastructure is then generated based upon the schedule supplied by the customer.

Some embodiments of the present invention generate the schedule. For example, a customer can supply the number of resources and the weighting of each. The schedule is then generated based upon the information supplied by the customer.

FIG. 1 shows a programmable resource scheduling system 100 for N resources, each of which may be available or unavailable, and a schedule having M slots, according to a preferred embodiment of the present invention. Programmable resourcescheduling system 100 comprises resources 102A-N, a scheduler 104, and a memory 106 comprising a scheduling data structure 108. According to a preferred embodiment of the present invention, scheduling data structure 108 comprises a plurality of records110A-M, one for each slot in the schedule, as described in detail below. Each record 110 comprises, for each of the N resources 102, an identifier of the next slot in the schedule allocated to the resource 102, and an identifier of the order in whichthe resources 102 occur in the schedule following the current slot.

A user can program scheduler 104 by providing a schedule having a plurality of slots each associated with one of resources 102. Embodiments of the present invention then create scheduling data structure 108 according to the schedule provided bythe user. Alternatively, the user can program scheduler 104 by providing scheduling information consisting of the number of slots, the number of resources 102, and a weight for each resource 102. Embodiments of the present invention then createscheduling data structure 108 according to the scheduling information provided by the user.

Scheduler 104 reads a record 110, and then selects the resource 102 indicated by the record 110. Scheduler 104 then selects another record 110 based on the current record 110 and which resources 102 are available, and then selects the resource102 indicated by the selected record 110. This process can repeat as desired. Because only one record 110 is required to determine the next schedule slot, only one read operation is required, rather than the multiple read operations required byconventional schedulers. Therefore scheduler 104 is much faster than conventional schedulers.

Now a data structure representing a schedule, and a method for generating the data structure, are described according to a preferred embodiment of the present invention. FIG. 2 shows an exemplary schedule 200 for N resources 202 comprising Mslots 204 where N=4 and M=15. FIG. 3 shows a data structure 300 representing schedule 200 of FIG. 2 according to a preferred embodiment of the present invention.

FIG. 4 shows a process 400 for generating data structure 300 of FIG. 3 according to a preferred embodiment of the present invention. Process 400 optionally generates schedule 200 based on information supplied by a customer (step 402). Forexample, the customer can supply the number of resources and the weight of each. Referring to the example of FIG. 2, the customer information indicates four resources (N=4) numbered 3, 2, 1, 0 and corresponding weights W.sub.3=8, W.sub.2=4, W.sub.1=2,W.sub.0=1. This information requires a schedule of M slots where

.times..times. ##EQU00008##

in which each resource N will appear W.sub.N times. Process 400 can generate schedule 200 according to any process. Embodiments of the present invention are not limited by the process by which schedule 200 is generated.

Referring again to FIG. 3, data structure 300 comprises M records 302A-M each representing a different one of the M slots 204 in schedule 200. Each record 302 comprises identifiers 304 of the N ones of the slots 204 in schedule 200 allocated toa next occurrence of a respective one of the N resources following the slot 204 represented by the record 302. In FIG. 3, the identifiers for resources N=3, 2, 1, 0 are labeled next_slot_3, next_slot_2, next_slot_1, and next_slot_0, respectively.

Each record 302 also comprises an identifier 306 of the order in which the N resources 202 occur in schedule 200 following the slot 204 represented by the record 302. In some embodiments, each identifier 306 comprises a sequence of N fields(referred to herein as a "bins") each comprising an identifier of one of the N resources. In FIG. 3, the bins are labeled, in order of occurrence of the identified resource 202 in schedule 200, bin0, bin1, bin2, and bin3.

Referring again to FIG. 3, for each record 302, process 400 also generates identifier 306 (step 406). For example, referring to FIG. 2, again consider slot 0 of schedule 200, which is allocated to resource 3. Following slot 0 in schedule 200,resources 3, 2, 1, 0 occur in the order 2, 3, 1, 0. In some embodiments, process 400 codes identifiers 306 as one-hot binary numbers, that is, binary number where only one bit is set. The code used in data structure 300 of FIG. 3 is shown in Table 1.

Process 400 therefore populates identifiers 306 of record 302A (which represents slot 0) of data structure 300 with the one-hot binary numbers for 2, 3, 1, 0 in sequence (that is, bin0=0100, bin1=1000, bin2=0010, bin3=0001). Recall that bin0identifies the closest resource in schedule 200, while bin3 identifies the resource that is most distant in schedule 200, from the current slot.

Embodiments of the present invention comprise apparatus, methods and software for using the data structures of the present invention to select resources. In some embodiments, the resources comprise buffers in a network switch implementing aplurality of QoS levels. FIG. 5 shows a data communications system 500 comprising a network switch 502 in communication with a network 504 according to a preferred embodiment of the present invention. While embodiments of the present invention aredescribed in the context of an output-queued switch, other embodiments can be used in other types of switches, as will be apparent to one skilled in the relevant arts after reading this description. And while embodiments of the present invention aredescribed with reference to a network switch, other embodiments can be implemented as routers, network interface controllers, and the like. Embodiments of the present invention that are implemented wirelessly are preferably compliant with at least oneof IEEE standards 802.11, 802.11a, 802.11b, 802.11g, 802.11n, 802.16, and 802.20. Furthermore, embodiments of the present invention are not limited to data communications, and can be used to schedule any sort of resources.

Network switch 502 comprises one or more input circuits 506 to receive packets of data from network 504, a forwarding engine 508 to forward the packets of data to one or more output queues 510, which deliver the packets to one or more respectiveoutput circuits 512 under the control of a respective scheduler 514. Each output queue 510 comprises 4 priority queues 520A-D. Output circuit(s) 512 transmit the packets to network 504. In some embodiments, each of the priority queues 520 storespackets of data having a respective QoS level. For purposes of explanation, assume that priority queues 520A-D store packets having priorities 0-3, respectively.

Scheduler 514 operates according to a data structure 518 stored in a memory 516. In some embodiments, data structure 518 has the structure described above with reference to data structure 300 of FIG. 3, and represents a schedule such as schedule200 of FIG. 2. For purposes of explanation, network switch 502 is described with reference to schedule 200 and data structure 300, where each resource represents one of the D priority queues 520A-D. Of course, network switch 502 can employ a datastructure representing different numbers of resources 202 and slots 204 than represented by data structure 300, as will be apparent to one skilled in the relevant arts after reading this description.

Scheduler 514 comprises a read circuit 522 to read the record 302 indicated by an index 524, a select circuit 526 to select the priority queue 520 allocated to the slot 204 represented by the record 302 read by read circuit 522, and an indexcircuit 528 to generate index 524 based on a previous record 302 read by read circuit 522. Index circuit 528 comprises an availability circuit 530 to determine which of priority queues 520 are available, that is, which of priority queues 520 containpackets to be transmitted. Index circuit 528 further comprises a next available queue circuit 532 to select the priority queue 520 that occurs next in schedule 200 based on the previous record 302, and a queue order circuit 534 to identify the record302 representing the next slot 204 allocated to the selected priority queue 520 based on the previous record 302.

FIG. 6 shows a process 600 for scheduler 514 of FIG. 5 according to a preferred embodiment of the present invention. When network switch 502 comprises multiple output queues 510, an independent process 600 is implemented for each output queue510. While embodiments of the present invention are described in the context of an output-queued switch, other embodiments can be used in other types of switches, as will be apparent to one skilled in the relevant arts after reading this description. And while embodiments of the present invention are described with reference to a network switch, other embodiments can be implemented as routers, network interface controllers, and the like. Furthermore, embodiments of the present invention are notlimited to data communications, and can be used to schedule any sort of resources.

Process 600 begins by resetting index 424 to zero (step 602). Read circuit 522 then reads the record indicated by index 324 (step 604). In the current example, the index=0, so read circuit 522 reads record 302A, which represents slot 0.

Process 600 determines whether any of priority queues 520 have packets to be transmitted, and if so, selects one of those priority queues 520 according to schedule 200 based only on the record 302 of data structure 518 that was read in step 604. Because only one record 302 is required per schedule slot, only one read operation is required, rather than the multiple read operations required by conventional schedulers. Therefore scheduler 514 is much faster than conventional schedulers, allowingnetwork switch 502 to operate at much higher speeds.

Index circuit 528 generates index 524 based on the record 302 read by read circuit 522, and based on the availability of priority queues 520. In particular, availability circuit 530 determines which priority queues 520 are available in outputqueue 510 (step 606), that is, which of priority queues 520 have packets to be transmitted. In some embodiments, each priority queue 520 asserts a respective availability signal 536 when that priority queue 520 has packets to be transmitted, andavailability circuit 530 determines which priority queues 520 are available based on availability signals 536. In other embodiments, availability circuit 530 polls priority queues 520 to determine availability.

Next available queue circuit 532 selects the available priority queue 520 that occurs next in schedule 200 based only on the previous record 302 (step 608). For example, referring to data structure 300 of FIG. 3, the current slot 204 is slot 0,which is represented by record 302A in data structure 300. Further assume that only priority queues 520B and 520D are available, representing packets having priorities 1 and 3, respectively. Referring to identifier 306 for record 302A in data structure300, the priorities occur in schedule 200 in the order 2, 3, 1, 0 following slot 0 (as described above, these values are coded as one-hot binary numbers in schedule 200). Because priority 3 occurs before priority 1, available queue circuit 532 selectspriority queue 520D, which corresponds to priority 3.

Select circuit 526 enables the priority queue 520 (520D in the example) selected by available queue circuit 532 (step 610). In some embodiments, select circuit 526 asserts a select signal 538 for the selected priority queue 520. In response,the selected priority queue 520 passes one or more packets of data to output circuit 512, which transmits the packet(s).

Queue order circuit 534 identifies the record 302 representing the next slot 204 allocated to the selected priority queue 520 (520D in the example) based only on the previous record 302, and generates index 524 representing the identified record302 (step 612). For example, continuing the example of data structure 300 of FIG. 3, assume that the current slot 204 is slot 0, which is represented by record 302A in data structure 300. Referring to identifier 304 in record 302A in data structure300, the next occurrence of priority 3 is in slot 2 (that is, next_slot.sub.--3=2 for record 302A). Queue order circuit 534 therefore generates a value for index 524 of index=2.

Read circuit 522 reads the record indicated by index 524 (resuming at step 604). In the current example, the index=2, so read circuit 522 reads record 302C, which represents slot 2. Process 600 can repeat to process schedule 200 as many timesas desired.

FIGS. 7A-7E show various exemplary implementations of the present invention. Referring now to FIG. 7A, the present invention can be implemented in a high definition television (HDTV) 712. The present invention may implement either or bothsignal processing and/or control circuits, which are generally identified in FIG. 7A at 713, a WLAN interface and/or mass data storage of the HDTV 712. The HDTV 712 receives HDTV input signals in either a wired or wireless format and generates HDTVoutput signals for a display 714. In some implementations, signal processing circuit and/or control circuit 713 and/or other circuits (not shown) of the HDTV 712 may process data, perform coding and/or encryption, perform calculations, format dataand/or perform any other type of HDTV processing that may be required.

The HDTV 712 may communicate with mass data storage 715 that stores data in a nonvolatile manner such as optical and/or magnetic storage devices. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller thanapproximately 1.8''. The HDTV 712 may be connected to memory 716 such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The HDTV 712 also may support connections with a WLAN via a WLANnetwork interface 717.

Referring now to FIG. 7B, the present invention implements a control system of a vehicle 718, a WLAN interface and/or mass data storage of the vehicle control system. In some implementations, the present invention implements a powertrain controlsystem 719 that receives inputs from one or more sensors such as temperature sensors, pressure sensors, rotational sensors, airflow sensors and/or any other suitable sensors and/or that generates one or more output control signals such as engineoperating parameters, transmission operating parameters, and/or other control signals.

The present invention may also be implemented in other control systems 722 of the vehicle 718. The control system 722 may likewise receive signals from input sensors 723 and/or output control signals to one or more output devices 724. In someimplementations, the control system 722 may be part of an anti-lock braking system (ABS), a navigation system, a telematics system, a vehicle telematics system, a lane departure system, an adaptive cruise control system, a vehicle entertainment systemsuch as a stereo, DVD, compact disc and the like. Still other implementations are contemplated.

The powertrain control system 719 may communicate with mass data storage 725 that stores data in a nonvolatile manner. The mass data storage 725 may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8''The powertrain control system 719 may be connected to memory 726 such as RAM, ROM, low latency nonvolatile memory such as flash memoryand/or other suitable electronic data storage. The powertrain control system 719 also may support connections with a WLAN via a WLAN network interface 727. The control system 722 may also include mass data storage, memory and/or a WLAN interface (allnot shown).

Referring now to FIG. 7C, the present invention can be implemented in a cellular phone 728 that may include a cellular antenna 729. The present invention may implement either or both signal processing and/or control circuits, which are generallyidentified in FIG. 7C at 730, a WLAN interface and/or mass data storage of the cellular phone 728. In some implementations, the cellular phone 728 includes a microphone 731, an audio output 732 such as a speaker and/or audio output jack, a display 733and/or an input device 734 such as a keypad, pointing device, voice actuation and/or other input device. The signal processing and/or control circuits 730 and/or other circuits (not shown) in the cellular phone 728 may process data, perform codingand/or encryption, perform calculations, format data and/or perform other cellular phone functions.

The cellular phone 728 may communicate with mass data storage 735 that stores data in a nonvolatile manner such as optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes oneor more platters having a diameter that is smaller than approximately 1.8''The cellular phone 728 may be connected to memory 736 such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. Thecellular phone 728 also may support connections with a WLAN via a WLAN network interface 737.

Referring now to FIG. 7D, the present invention can be implemented in a set top box 738. The present invention may implement either or both signal processing and/or control circuits, which are generally identified in FIG. 7D at 739, a WLANinterface and/or mass data storage of the set top box 738. The set top box 738 receives signals from a source such as a broadband source and outputs standard and/or high definition audio/video signals suitable for a display 740 such as a televisionand/or monitor and/or other video and/or audio output devices. The signal processing and/or control circuits 739 and/or other circuits (not shown) of the set top box 738 may process data, perform coding and/or encryption, perform calculations, formatdata and/or perform any other set top box function.

The set top box 738 may communicate with mass data storage 743 that stores data in a nonvolatile manner. The mass data storage 743 may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may bea mini HDD that includes one or more platters having a diameter that is smaller than approximately 1.8''The set top box 738 may be connected to memory 742 such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitableelectronic data storage. The set top box 738 also may support connections with a WLAN via a WLAN network interface 743.

Referring now to FIG. 7E, the present invention can be implemented in a media player 744. The present invention may implement either or both signal processing and/or control circuits, which are generally identified in FIG. 7E at 745, a WLANinterface and/or mass data storage of the media player 744. In some implementations, the media player 744 includes a display 746 and/or a user input 747 such as a keypad, touchpad and the like. In some implementations, the media player 744 may employ agraphical user interface (GUI) that typically employs menus, drop down menus, icons and/or a point-and-click interface via the display 746 and/or user input 747. The media player 744 further includes an audio output 748 such as a speaker and/or audiooutput jack. The signal processing and/or control circuits 745 and/or other circuits (not shown) of the media player 744 may process data, perform coding and/or encryption, perform calculations, format data and/or perform any other media playerfunction.

The media player 744 may communicate with mass data storage 749 that stores data such as compressed audio and/or video content in a nonvolatile manner. In some implementations, the compressed audio files include files that are compliant with MP3format or other suitable compressed audio and/or video formats. The mass data storage may include optical and/or magnetic storage devices for example hard disk drives HDD and/or DVDs. The HDD may be a mini HDD that includes one or more platters havinga diameter that is smaller than approximately 1.8''The media player 744 may be connected to memory 750 such as RAM, ROM, low latency nonvolatile memory such as flash memory and/or other suitable electronic data storage. The media player 744 also maysupport connections with a WLAN via a WLAN network interface 751. Still other implementations in addition to those described above are contemplated.

Embodiments of the invention can be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Apparatus of the invention can be implemented in a computer program product tangiblyembodied in a non-transitory tangible computer readable storage medium for execution by a programmable processor; and method steps of the invention can be performed by a programmable processor executing a program of instructions to perform functions ofthe invention by operating on input data and generating output. The invention can be implemented advantageously in one or more computer programs that are executable on a programmable system including at least one programmable processor coupled toreceive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. Each computer program can be implemented in a high-level procedural or object-orientedprogramming language, or in assembly or machine language if desired; and in any case, the language can be a compiled or interpreted language. Suitable processors include, by way of example, both general and special purpose microprocessors. Generally, aprocessor will receive instructions and data from a read-only memory and/or a random access memory. Generally, a computer will include one or more mass storage devices for storing data files; such devices include magnetic disks, such as internal harddisks and removable disks; magneto-optical disks; and optical disks. Storage devices suitable for tangibly embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks; and CD-ROM disks. Any of the foregoing can be supplemented by, or incorporated in, ASICs(application-specific integrated circuits).

A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations arewithin the scope of the following claims.